Not to be insulting but I must LOL at this suggestion. I believe more education around the consequences of using a knife, workshops that show real knife wombs of dead and living people, testimonies of victims and perpetrators of knife injuries.

Like sum gun buy program you mostly going to get non crime used guns. Same with knives you most will only get knives from people who don't commit crimes, plus you might just drive up knife purchases if you offer $20 gift card. Someone might get the gift sell it for $20 or go buy $20, go buy a 10.00 knife and keep the ten. Real criminals and so call gangstas won't turn in their weapons they need them to bring to harm to someone or protect themselves from being harmed.

"Boston Public Schools spokesman Brian Ballou said the stabbing did not involve anyone at the school and occurred some 45 minutes after classes were dismissed."

So somebody gets stabbed in front of a school, after classes are over, in what's objectively a fairly rough neighborhood of Boston, and that's cause to boycott the entire district except for two schools you deem acceptable. Makes sense.